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lltc following Group O commands are supponed:
9yte0
(o,c111doacode)
OOH
OUI
08H
OAH
IBH
OJH
mtlTataaitratdy
Tenunitready
Reurounit
Read
Write
S1an/Stopuni1
Request sense
Allows
1he ini1ia1or to verify thlll 1he player
is
running, the disc is
logged in, and 1hat 1he player is ready for command! from the initiator
lhrough lhe logic unit selected by the hos!.
If lhe volume associated to that bgic unit is
open
lhe
n the ~atui; byte
retumed will be 0.
If
1he logic unit is not
open,
01
1he
target is not
ready,
the
s1atus byte will be 02H. More detailed information can be
oblained using
a
Request sense oommand
(OJH)
tlHRnenult
Displays
the lo
peal
picture
iero of
the vo
lume
llut
i$ aoces.sed thtouah
the
logic uni1 number
of the comma
nd.
If
wcccsslut, the
status
~turned is
0;
otherwise
the smu
1
returned is
02H.
"""""
Allows 1he
initia
tor 10 read blocks of data from
1he
disc. The
block
n•mber
of
the firslblock tobe read
is
a logicalblockaddres.s..
and
is
reb.live
lo
the
beginning of the d.ita of
the selected
volume. There is an
ofbe
t between the logical blocks within a volume
a
nd the physical
blotbon the disc. This offset is added by
LV-DOS
1o the logical block
address,
thus
ma
king 1he physical
loca
tion of a volume on a disc
1ransp,are
n11otheinitia10r.
If
MK.Ctu.ful.
a stalus of O is n:lumed; otherwise 02H
is
returned. A
subseq
~nl Request sense data command
reveals
inme information
such as ·unit no\
ready'
or
'media
error'.
A MUI•
phase:
is
required to
read the logical
block(s).
In
seareti
mode
RI
(see late
r in
1his
section)
this
command cause,
the
video
1o swi1eh off,
sinu
after
a
search
the syste
m will stop at
a rando
m
pK:111,e. The
video
will
also
be
swi1ched
off
if
the reqvestcd
data
is
in
cac:hi:.
In
seari:h
mode
RO
the
video
is o
nly
muled
cturin1 dala rclritval,
afler which the
previo us displa
yed piclure
is
shown.
OA.HWrik
'The
Write
command is implemen1ed so that
1he sys1e
m may
be
used
wilh
o perating
syi;tems lhat
perform.
for
n.ample
.
lime: and date
st"rlfMng
o
n file level when a
file
has been
accessed.
To prevent error
messages from
the
operating system,
wri1e
cominands are
irlplcmc:nted as dummy write co11mands wilhouc dala
being
written to
a
medium. Consequently communication is
e
nabkd with operaling
systems
with driveri for read/\oorite media without patching of the
openu ing
l
yste
m. If successful, a status ofO
is
returned;
otherwise 02H
is
re1umed
.
A
dala oat phase is required unless the number of da1a
bkxksspeci(ied in
the
eommand
is iero
.
I B H ~ t
BitOol byte
I
•
I
.
Bit0ofbyte
4
"'
I
fo
rSwt...tt.1ndOfo
r
Sl~ait.
In
rc~
se
to the Stop-unit
comma
nd,
the
disc
is
logged
off,
volumes
close down.
and
the pla yer
goes
inlo 1he
stand
by
mode.
A
ll
swi1ches
are
reset to
their default
condilions
e.g. fron1 panel
conuols
enabled
,
CIC.
1be
Slop-unit
command
is always
executed
without e
rror
status.
An additional ' Eject'
comma
nd
is
required if lhe disc has to be
changed.
The
S1an,unit command logs .1 disc on to L
V·OOS a
nd
as
such gives a
means
10 perform a disc reset to default. Logging on means that the
system1.1ble
will be read from the disc and 1ha1
YO!u
mesare opened. If
dte Stan-unit command
is
succcaful, the
status
byte isO; 01herwise 1he
sta1us
byte is 02H
(sense key •
2 for ·unit not
ready').
39
If
the disc has been
replaced.
or a S1op-unit:eommand
issued,
then a
Start-unit command m~ be issued to ensure 1h11
L
V-DOS
is logged
on. If for
a
ny reason the Stan-unit command
fails,
LV-DOS
will
respond with
a
·check
condi1ion·
status byte and a
Reqvest
scnw
command will
have
either unse key
•
02
(unit
not ready) if the
drive
is
physic.ally
not
read~.
o
r
sense kty
"' 03
(media error)
if
the drive
is
spinnin&
but no
dall
can
be rtad rrom the
disc.
It is
mandatory
that
lhese commands are used
if
the media
~
10
be
changed.
They
can be iiSUCd lo any logicunil, open or closed. The
Test
unit ready C0111mand can be used lo determine
whe
ther lhe player
is
ready with the disc
nm11ing
or not.
O J H R ~ -
Allows the
initiaCOf lo
ob1ain more detailed information
.1bou1
1he
execution
of
the previous command to the specified
log.C
unit,
regardless
ol
whether it was succeuful or not.
If a command
is
executed for a specified logic unit
,
the
relevan1
sense
information is s10ted and will be available for a
subseque
nt Req~
sense
command
for
1hat
logic
unit
o nly.
In 01her words, separate
sense
da1a
is
main1a
trted
for
each logic
unit.
Tbi5
command can
be
issued
to
any Josic
unit,
open
or closed.
It will
alwa
ys
be exea,red wi1t.ou1
enor
s1a1us.
A ......
phue
is
req11ired
toread1hesense data
The
fourth
rommand
byte
specifies
the
allocatio
n length for the sense
data in the hon;
1his
byte should be set to zero.
NOIHX!nikd- 4ela (length 4 bytes) will be returned.
Dlltafo~:
(MS
bit)
.,
..
0
Valid
ErrordliS(O)
Enorcode
Logic W1ilt111mber
Logicalblockaddres.s (MSB)
Lop<:alblotk
addre»
Logicalblotk
address (LSB)
(LS
bit)
The
•did bit
j5
1
if
lhe logical block address bytes
a
re valid
(indicating
theblock
where1heerror occurred).
L V-DOS suppcins 1he
fo
llowing enor codes (in hex):
•
D
No erro
r
Unil
not ready
Mediaenor
Hardwa
re
e
n
or
IUep
lrequell
Commancl aboned
Volume
exceeded
0
No
en...-
No
e rror
meaM
lhal the
previous command
was
carried
o•I
eorrec,Jy.
Unit nol
ready
means lhll there
is no
volume associated with
the
specified
logic
unit after
a
Test unit ready, Read or Write
command.
This
reply
will
also
occur after
a
S1an-unil command has failed
beca1a1e
the drive
is physically
no1
ready (no disc, no1 spinning etc.).
Media
enor
occurs
if
it 1$
not possible to read data from Che
disc,
eilher
afte
r
a
Stan•unil COt'l\inand when
1he
dise
is
CLV or CAV wilho\it
dia.(tal
da
ta.
o
r
when
ii
is
auemp1ed
10
read
from
a
loged
on
disc
of
the
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